Ketoconazole slows how the body clears Ceritinib, so more Ceritinib builds up in your body. Ketoconazole should be avoided while you take Ceritinib.
These medicines can affect each other in a serious way. Do not start taking them together unless your doctor has said it is OK. If you already take both, do not stop either one on your own: speak to your doctor or pharmacist soon.
What to do: Do not take them together unless your doctor has said so. Do not stop either medicine on your own; ask your doctor first.